Re: [PATCH] swiotlb: avoid double copy with swiotlb on tx socket

[kernel test robot <lkp@intel.com>]

Hi Luigi,

kernel test robot noticed the following build warnings:

[auto build test WARNING on akpm-mm/mm-everything]
[also build test WARNING on linus/master v7.1 next-20260615]
[cannot apply to driver-core/driver-core-testing driver-core/driver-core-next driver-core/driver-core-linus]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Luigi-Rizzo/swiotlb-avoid-double-copy-with-swiotlb-on-tx-socket/20260616-074655
base:   https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-everything
patch link:    https://lore.kernel.org/r/20260615234220.3946885-1-lrizzo%40google.com
patch subject: [PATCH] swiotlb: avoid double copy with swiotlb on tx socket
config: loongarch-allnoconfig (https://download.01.org/0day-ci/archive/20260616/202606161519.z7SY98jp-lkp@intel.com/config)
compiler: clang version 20.1.8 (https://github.com/llvm/llvm-project 87f0227cb60147a26a1eeb4fb06e3b505e9c7261)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260616/202606161519.z7SY98jp-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202606161519.z7SY98jp-lkp@intel.com/

All warnings (new ones prefixed by >>):

>> mm/page_alloc.c:721:17: warning: unused variable 'folio' [-Wunused-variable]
     721 |                 struct folio *folio = (struct folio *)page;
         |                               ^~~~~
   1 warning generated.
--
>> Warning: kernel/dma/swiotlb.c:95 cannot understand function prototype: 'atomic_t global_device_serial = ATOMIC_INIT(0);'
>> Warning: kernel/dma/swiotlb.c:2087 function parameter 'where_debug_only' not described in 'swiotlb_free_pages'
>> Warning: kernel/dma/swiotlb.c:2087 function parameter 'where_debug_only' not described in 'swiotlb_free_pages'


vim +/folio +721 mm/page_alloc.c

   717	
   718	void swiotlb_destroy_compound_page(struct page *page, unsigned int order)
   719	{
   720		if (order > 0) {
 > 721			struct folio *folio = (struct folio *)page;
   722	
   723			__ClearPageHead(page);
   724			page[1].flags.f &= ~PAGE_FLAGS_SECOND;
   725	#ifdef NR_PAGES_IN_LARGE_FOLIO
   726			folio->_nr_pages = 0;
   727	#endif
   728			for (int i = 1; i < (1 << order); i++) {
   729				page[i].mapping = NULL;
   730				clear_compound_head(&page[i]);
   731			}
   732		}
   733	}
   734	#endif /* CONFIG_SWIOTLB */
   735	

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